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Question

Mathematics of Natural Selection Quick Check
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Question
Paleontologists observed changes in the sizes of black bears as their environment changed. During warmer periods between ice ages, most black bears were small. During ice ages, most black bears were large. Which type of selection is this, and how would a graph of the distribution curve of black bear size change as Earth moved out of an ice age?(1 point)
Responses

disruptive; the curve would break into two peaks with a dip in the middle
disruptive; the curve would break into two peaks with a dip in the middle

directional; the curve would shift to the right
directional; the curve would shift to the right

stabilizing; the curve would become taller in the middle and shorter on each side
stabilizing; the curve would become taller in the middle and shorter on each side

directional; the curve would shift to the left
directional; the curve would shift to the left
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Answer 1

The situation you described regarding the size of black bears in relation to changing environmental conditions during ice ages and warmer periods indicates a pattern of directional selection. This is because there are two different prevalent traits (large bears during ice ages and small bears during warmer periods), and as conditions change, one trait becomes more favorable than the other.

As the Earth moves out of an ice age and into a warmer climate, we would expect the distribution curve of black bear size to shift towards the smaller size, reflecting the increased frequency of smaller bears.

Therefore, the correct response would be:

directional; the curve would shift to the right.